Olefin polymers are used in a wide variety of products, from sheathing for wire and cable to film. Olefin polymers are used, for instance, in injection or compression molding applications, in extruded films or sheeting, as extrusion coatings on paper, for example photographic paper and digital recording paper, and the like. Improvements in catalysts have made it possible to better control polymerization processes, and, thus, influence the properties of the bulk material. Increasingly, efforts are being made to tune the physical properties of plastics for lightness, strength, resistance to corrosion, permeability, optical properties, and the like, for particular uses. Chain length, polymer branching and functionality have a significant impact on the physical properties of the polymer. Accordingly, novel catalysts are constantly being sought in attempts to obtain a catalytic process which permits more efficient and better controlled polymerization of olefins.
Conventional polyolefins are prepared by a variety of polymerization techniques, including homogeneous and heterogeneous polymerizations. Certain transition metal catalysts, such as those based on titanium compounds (e.g., TiCl.sub.3 or TiCl.sub.4) in combination with organoaluminum cocatalysts, are used to make linear and linear low density polyethylenes as well as poly-.alpha.-olefins such as polypropylene. These so-called "Ziegler-Natta" catalysts are quite sensitive to oxygen and are ineffective for the copolymerization of nonpolar and polar monomers.
Recent advances in non-Ziegler-Natta olefin polymerization catalysis include the following:
L. K. Johnson et al., WO Patent Application 96/23010, disclose the polymerization of olefins using cationic nickel, palladium, iron, and cobalt complexes containing diimine and bisoxazoline ligands. This document also describes the polymerization of ethylene, acyclic olefins, and/or selected cyclic olefins and optionally selected unsaturated acids or esters such as acrylic acid or alkyl acrylates to provide olefin homopolymers or copolymers.
European Patent Application No. 381,495 describes the polymerization of olefins using palladium and nickel catalysts which contain selected bidentate phosphorous containing ligands.
L. K. Johnson et al., J. Am. Chem. Soc., 1995, 117, 6414, describe the polymerization of olefins such as ethylene, propylene, and 1-hexene using cationic .alpha.-diimine-based nickel and palladium complexes. These catalysts have been described to polymerize ethylene to high molecular weight branched polyethylene. In addition to ethylene, Pd complexes act as catalysts for the polymerization and copolymerization of olefins and methyl acrylate.
G. F. Schmidt et al., J. Am. Chem. Soc., 1985, 107, 1443, describe a cobalt(III) cyclopentadienyl catalytic system having the structure [C.sub.5 Me.sub.5 (L)CoCH.sub.2 CH.sub.2 -.mu.-H].sup.+, which provides for the "living" polymerization of ethylene.
M. Brookhart et al., Macromolecules, 1995, 28, 5378, disclose using such "living" catalysts in the synthesis of end-functionalized polyethylene homopolymers.
U. Klabunde, U.S. Pat. Nos. 4,906,754, 4,716,205, 5,030,606, and 5,175,326, describes the conversion of ethylene to polyethylene using anionic phosphorous/oxygen donors ligated to Ni(II). The polymerization reactions were run between 25 and 100.degree. C. with modest yields, producing linear polyethylene having a weight-average molecular weight ranging between 8K and 350K. In addition, Klabunde describes the preparation of copolymers of ethylene and functional group containing monomers.
M. Peuckert et al., Organomet., 1983, 2(5), 594, disclose the oligomerization of ethylene using phosphine/carboxylate donors ligated to Ni(II), which showed modest catalytic activity (0.14 to 1.83 TO/s). The oligomerizations were carried out at 60 to 95.degree. C. and 10 to 80 bar ethylene in toluene, to produce linear .alpha.-olefins.
R. E. Murray, U.S. Pat. Nos. 4,689,437 and 4,716,138, describes the oligomerization of ethylene using phosphinelsulfonate donors ligated to Ni(II). These complexes show catalyst activities approximately 15 times greater than those reported with phosphine/carboxylate analogs.
W. Keim et al., Angew. Chem. Int. Ed. Eng., 1981, 20, 116, and V. M. Mohring et al., Angew. Chem. Int. Ed. Eng., 1985, 24, 1001, disclose the polymerization of ethylene and the oligomerization of .alpha.-olefins with aminobis(imino)phosphorane nickel catalysts.
G. Wilke, Angew. Chem. Inmt. Ed. EngI., 1988, 27, 185, describes a nickel allyl phosphine complex for the polymerization of ethylene.
K. A. O. Starzewski et al., Angew. Chem. Int. Ed. Engl., 1987, 26, 63, and U.S. Pat. No. 4,691,036, describe a series of bis(ylide) nickel complexes, used to polymerize ethylene to provide high molecular weight linear polyethylene.
WO Patent Application 97/02298 discloses the polymerization of olefins using a variety of neutral N, O, P, or S donor ligands, in combination with a nickel(0) compound and an acid.
Brown et al., WO 97/17380, describes the use of Pd .alpha.-diimine catalysts for the polymerization of olefms including ethylene in the presence of air and moisture.
Fink et al., U.S. Pat. No. 4,724,273, have described the polymerization of .alpha.-olefins using aminobis(imino)phosphorane nickel catalysts and the compositions of the resulting poly(.alpha.-olefins).
Additional recent developments are described by Sugimura et al., in JP 96-84344, JP 96-84343, and WO 9738024, and by Yorisue et al., in JP 96-70332. Moreover, the University of North Carolina and Du Pont have reported the polymerization of olefins using neutral nickel catalysts in WO 9830609 and WO 9830610.
Notwithstanding these advances in non-Ziegler-Natta catalysis, there remains a need for efficient and effective Group 8-10 transition metal catalysts for effecting polymerization of olefins. In addition, there is a need for novel methods of polymerizing olefins employing such effective Group 8-10 transition metal catalysts. In particular, there remains a need for Group 8-10 transition metal olefin polymerization catalysts with both improved temperature stability and functional group compatibility. Further, there remains a need for a method of polymerizing olefins utilizing effective Group 8-10 transition metal catalysts in combination with a Lewis acid so as to obtain a catalyst that is more active and more selective.